What does X-Cache: Hit from Backend mean?

Question

I looked all over the internet but can't seem to find out what this means. I think it might be the cause of an error I'm currently getting in which the page refuses to update its references to certain files in my symfony application.

I looked into X-Cache but I do not have it installed on my system, I'm using OpCache though.

Answer 1

Check this link, http://ageekandhisblog.com/cloudflare-the-cdn-that-saves-your-server/. In short you see this header because CloudFlare is on.